There are major accumulations of heavy oils and bitumens at a number of global locations, including, Canada, U.S.A. and Venezuela. Reserves of these crude oils have been estimated at over 100 billion barrels in Canada and the United States and over 3 trillion barrels in Venezuela. These vast resources remain largely untapped for want of commercially viable recovery procedures.
The bitumen may be in the form of oil sands. Oil sands are basically a mixture of bitumen, mineral and water of variable bitumen content. Only those surficial deposits in the Athabasca region of Alberta, Canada are being exploited on a commercial scale at this time. In the deposits, the bitumen content varies up to 18 wt.% and averages about 12 wt.%, water is usually about 3 to about 6 wt.% and the mineral content, predominantly quartz, ranges from about 84 to about 86 wt.%.
At the present time there is one commercial procedure for the recovery of bitumen from these deposits, known as "hot water" process. The latter procedure involves interconnected steps of feed conditioning, bitumen separation, waste disposal and bitumen concentrate cleaning.
The "hot water" process suffers from several drawbacks which currently are tolerated for lack of a viable commercial alternative. A major disadvantage involves the discharge of a tailings stream, which, after removal of sand, settles in ponds to an upper aqueous layer containing less than 5% clay solids which is reusable in the plant and a lower slimes layer containing 5 to 30% clay solids which is extremely difficult to separate into its solids and water components and is not reusable as such.
The net volume of tailings produced by the hot water process in the form of sand and slimes amounts to about 40% greater in volume than the mined tar sand, thus representing a serious backfill problem.
Another disadvantage of the hot water process is that it can be applied satisfactorily only to mined oil sands. The mining of oil sands requires the use of expensive large scale earth-moving equipment to remove overburden to expose the oil sands, the use of expensive large scale mining equipment to remove the oil sand and the use of conveying systems to convey the mined oil sand to the plant site. The mining of oil sands is only practical with surficial deposits.
Heavy crude oils are highly viscous and proposals for mining the same rely mainly on heating the oil to decrease its viscosity and render it flowable for recovery from its deposit and upgrading. The energy requirement for such operations is very high, estimated to be the consumption of one barrel of oil for each barrel recovered.
Numerous proposals have been made for improving the economics of recovery of heavy crude oils and bitumens and for alleviating the prior art problems of the commercial hot water process. As far as the inventor is aware, none of such proposals has been implemented.
One such proposal is outlined in U.S. Pat. No. 2,288,857 which describes the formation of an oil-in-water emulsion from the bitumen to facilitate recovery from the formation. The emulsion is subsequently described as being broken to recover the bitumen. This prior art procedure is attractive since the bitumen is converted to a form which renders the same more readily pumpable without the necessity for the considerable energy input to heat the oil to decrease its viscosity. Traditionally emulsions formed from bitumen have been considered undesirable in that they were thought to be extremely stable and, therefore, difficult to separate.
A further patent which describes emulsion formation from bitumen is U.S. Pat. No. 2,882,973 which indicates that the use of a combination of a non-ionic surfactant and alkali is essential for emulsification to be effected. Emulsion separation to recover the bitumen again is described. The use of non-ionic surfactants is highly undesirable in view of their cost and the fact that they are non-recoverable upon emulsion breaking.